1. Field of the Invention
The present invention relates to a battery module and in particular relates to a battery module comprising a plurality of battery cells employing non-aqueous electrolyte, typified by for example lithium ion batteries.
2. Description of the Related Art
In recent years, non-aqueous secondary batteries, in particular, lithium ion secondary batteries, have attracted attention as for example power sources for cordless portable electronic equipment and, in addition, as power sources for driving vehicles, such as for example electric automobiles, on account of their high voltage and high energy density.
For example, as the power source for vehicle mounting that is employed in an electric automobile or an electric car, for improving versatility, a battery module may be constituted by connecting a plurality of battery cells in series or parallel, and installing a plurality of these battery modules in combination as a battery pack.
For example, Laid-open Japanese Patent Application No. Tokkai 2001-93484 (hereinbelow referred to as Patent Reference 1), discloses a secondary battery assembly in which a secondary battery is constituted by arranging in series a plurality of single cells, this plurality of series-arranged single cells being arranged in a cooling box, wherein coolant passages are formed between the inside wall surface of the cooling box and the side faces of the single cells and between the single cells.
Thus, in such a battery module having a plurality of single cells, it is necessary to fix the cells in order to prevent adjacent cells from coming into contact due to vibration etc.
Furthermore, when a plurality of battery cells are arranged next to each other as described in the above Patent Reference 1, the battery cells may swell up due to evolution of gas etc in the interior of the sealed cells during power generation, causing adjacent battery cells to come into contact. For reasons such as preventing penetration of water, the outer container of the battery cells is frequently formed of metal and this sometimes results in short-circuiting when adjacent battery cells come into contact. To prevent this, conventionally, insulation of the battery cells was effected by means such as covering the outer container of the battery cells with insulating material. An example is to be found in Laid-open Japanese Patent Application No. Tokkai 2003-197158 (hereinbelow referred to as Patent Reference 2).
However, when the surface of the outer container of the battery cells is covered with electrically insulating material, this electrically insulating material functions as a thermally insulating layer, making it necessary to provide powerful cooling means.